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Abstract:

In (E)-1-(4-methyl-2-nitrobenzenethiolato)-2-phenylethene,
C15H13NO2S (1) (orthorhombic Pbca), the nitro group is
almost coplanar with the adjacent aryl ring, but the dihedral
angles between the nitro-aryl and styryl fragments is 121 .
The molecules are linked by paired C?H O hydrogen
bonds in a chain of rings. In S-(2-nitrophenyl)benzenecarbothiolate,
C13H9NO3S (2) (monoclinic P21/a), the nitro
group is rotated by 33.0 (2) out of the plane of the adjacent
aryl ring and the thiobenzoate group is strongly twisted away
from the plane of the disubstituted aryl ring. The molecules of
(2) are linked into chains by C?H O hydrogen bonds, and
each chain is linked to two neighbouring chains by means of
aromatic stacking interactions. In 1-(2-nitrophenylthio)-
2,5-pyrrolidinedione, C10H8N2O4S (3) (monoclinic P21/a), the
nitro group is again almost coplanar with the adjacent aryl
ring, but the pyrrolidinedione unit is almost orthogonal to the
O2NC6H4SN plane. There are three types of C?H O
hydrogen bond in the structure, and these link the molecules
into a two-dimensional net. The conformations of these
molecules have been investigated by SCF calculations and two
energy minima have been identi?ed for each: the molecules of
(1) and (3) adopt conformations in their crystals which are
close to those at the overall energy minima calculated for
isolated molecules, while molecules of (2) adopt a conformation
in the crystal close to that calculated for the local energy
minimum. Comparisons are made with the structures of some
related compounds and it is concluded that, while the nature
of the two conformational minima is determined by intramolecular
forces, the choice between them is determined
primarily by intermolecular forces.